1. Field of the Invention
The present invention relates to a communication apparatus, and more particularly to communication apparatus and communication method having a memory transmission function to transmit input image data after having temporarily stored the image data.
2. Related Background Art
A facsimile apparatus has been known as a communication apparatus.
Recently, since it has been common in the facsimile apparatus to use a roll paper as a record sheet, a sending station transmits image data read from one sheet of document sheet as one page of image data without regard to a length of the image data along a sub-scan direction of the read document sheet.
However, recently, cut sheets are frequently used as record sheets. When a document sheet which is shorter in length than the cut sheet is to be transmitted and when the image data read from one sheet of document sheet is transmitted as one page of image data without regard to the sub-scan direction length of the image data of the read document sheet as it is in the prior art, the image data is recorded only in an upper portion of the cut sheet at a receiving station and a large blank area is left at a bottom portion and the record sheet is wasted. In addition, when received multi-page image data is to be recorded, it is necessary to feed the sheets for the blank areas and it damages the speed of record and increases a running cost.
A prior art facsimile apparatus has a memory transmission function to read multi-page document sheet images, temporarily store the read image data and transmit the stored image data of the memory to a predetermined destination station. In such a memory transmission function, image data of P1 and P2 of a document sheet 31 as shown in (A) in FIG. 8 is read, stored in a memory page by page, and the stored image data is transmitted page by page by a communication protocol shown in (B) in FIG. 8. In this communication protocol, the image data 32-1 corresponds to the image of P1 and the image data 32-2 corresponds to the image of P2, and the image data is transmitted serially page by page by the communication protocol.
As a result, even if the sub-scan direction length of the images drawn on P1 and P2 of the transmission document sheet 31 is short and the amount of images of the two pages is less than the amount of image of one page of the cut sheet as shown in (C) in FIG. 8, blank areas are created on P1 and P2 of the received document sheet 33 if the destination station apparatus receives the image while using the cut record sheets and the received document sheets are wasted.
Further, since the P1 and P2 having small amount of data per page are serially transmitted page by page, the over all communication time T1 is increased by a page-to-page communication protocol, that is, by protocol for MPS (multi-page signal) and MCF (message confirmation) and the communication efficiency is lowered accordingly.
In order to solve the above problems, it has been proposed (U.S. patent application Ser. No. 08/691,680) to store image data inputted by a CCD scanner in a memory, determine the number of lines available for recording per page while taking size information of the record sheet acquired from the receiving station into consideration, combine continuous multiple pages of image data within the range of the number of available lines for recording and transmit it as one page of image data.
The proposed system is outlined below.
When continuous pages of image data having short sub-scan length as shown by P1 and P2 of a document sheet 31 of (A) in FIG. 9 is stored in a memory for transmission, the read data 32-1 and 32-2 of P1 and P2 of the document sheet 31 as shown in (B) in FIG. 9 are combined in terms of communication protocol into one page of image data, which is transmitted to the destination station apparatus. Thus, the communication protocol required between pages is omitted to shorten the communication time T2, and even if the receiving station apparatus uses the cur sheets as shown in (C) in FIG. 9, one page of received document sheet free of blank is acquired. It should be noted that the communication time T1 shown in FIG. 8 is longer than the communication time T2 shown in FIG. 9.
In this method, the record sheets may be saved and the rapid recording is attained so that the running cost is reduced, but when the multiple page of image data having different resolutions are combined and transmitted, they are recorded in different status from that of the original images at the receiving station.
Specifically, it is assumed that a first page of image data is read and stored at a standard resolution (3.85 lines/mm) and a second page of image data is read and stored at a high resolution (7.7 lines/mm), and those two pages of image data are combined and transmitted by declaring a standard resolution as a transmission resolution. In this case, since the receiving station decodes the two pages of image data as one page of image data and records it, the first page of image data is stored normally but the second page of image data is recorded while it is stretched by a factor of two in the sub-scan direction.
Conversely, when the high resolution is declared as the transmission resolution, the second page of image data are transmitted normally but the first page of image data is recorded while it is reduced to by a factor of xc2xd.
A prior art facsimile apparatus stores one page of read image data in a memory, reads the image data stored in the memory for transmission, erases the transmitted page of image data and stores newly read page of image data in the memory space in which the erased page of image data has been stored.
When multiple page of read image data are to be combined into the page for transmission in such a system, the following problems occurs.
First, before the reading of the last page of the image data of the transmission document sheet into the memory is completed, the transmission of the image data already stored in the memory is started. When the image data of the short sub-scan length page is then read into the memory, the image data of this page might be combined with the image data of the next page so that the process waits until the reading of the image data of the next page into the memory is completed, and then the sub-scan lengths of the image data of the both pages are summed. If the total sub-scan length is within a predetermined length, the both image data are combined into one page of image data for transmission to the destination station, and after the completion of the transmission, the transmitted one page of image data is erased from the memory. However, when an available capacity remaining in the memory (hereinafter simply referred to as a remaining capacity) is small, the memory becomes full during the reading of the image data of the next page and the image data of less than one page might be transmitted.
Namely, in order to assure the transmission of the image data of the short sub-scan length page by combining it with the image data of the next page as one page of image data, it is required to wait for the determination of the sub-scan length of the image data of the next page to be read next. Thus, when the remaining memory capacity is small, the memory becomes full and the length of the image data of the next page is not determined so that the transmission is not attained.
It is an object of the present invention to improve a communication apparatus and a communication method.
It is another object of the present invention to improve a facsimile apparatus and a facsimile communication method.
It is still another object of the present invention to prevent image data of different resolutions from being directly combined and recorded on one record sheet while it is partially expanded or reduced.
It is still another object of the present invention to provide a facsimile apparatus which shortens the communication time by combining multiple pages of image data having a short sub-scan length, stored in a memory, into one page of image data for transmission while minimizing a possibility of the memory transmission disable due to the memory full.